Calculating Impulse from a Graph: How to Solve the Problem

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To calculate impulse from a graph, it is effective to divide the graph into distinct areas, typically triangles, representing positive and negative impulses. Impulse is defined as the change in momentum, which can be expressed through the relationship between force and time. The integral of force over time gives the total impulse, with areas below the x-axis contributing negatively. Each area should be calculated separately and then combined to find the total impulse. This method ensures accurate accounting of both positive and negative contributions to impulse.
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[The problem is in the attached image]


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The Attempt at a Solution


My best guess is to break up the graph into two triangles one positive, one negative and then calculate and add the impulse of both of these triangles... Is that what you're supposed to do?
 

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Impulse is defined as the change in momentum, or Δp=Δ(mv)=mΔv. This quantity is related to the force F by the following logic.

F = dp/dt (you should memorize this equation; it's very useful.)

= d(mv)/dt
= m(dv)/dt
= m(dv/dt)
= ma, which is the definition of force.

Given this simple relationship,

∫dp = Δp = ∫F dt

What is an integral? An integral is the signed area between the x-axis (F=0) and the curve. So yes, calculate them separately, and then glue them together. Don't forget that everything below F=0 counts as negative impulse.
 
Thank you :)
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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